I was wondering what method of data collection would be best for this scenario. I have a statistics project that I intend to use this in.

Fast-food chains are known for upselling meals. crew members are trained to prompt questions like "was that in a large meal today?"

my experiment is to put to this to the test to see if this technique works. I work as a crew member at a fast food company so I am able to collect this data during my shifts. But what would be the correct way for data collection in this scenario. If I have missed any details please let me know as I really need to get this right.

Thanks in advance!!